1. Field of the Invention
The present invention relates to encoding and decoding of image data, and more particularly, to an apparatus and a method for encoding and decoding an image containing a gray alpha channel image.
2. Description of the Related Art
A gray alpha channel image serves as a mask to select a specific zone in a general image. The ISO/IEC MPEG-4 standard provides a method of encoding an image in units of objects in which shape information is separately encoded so that the image is identified in the units of the objects. The shape information may be considered as a gray alpha channel image. However, since, in the MPEG-4 standard, the shape information is encoded in a different manner from general images, it is difficult to realize an apparatus for encoding an image containing a gray alpha channel image and to process the shape information in real time due to the significant amount of calculations required.
According to the H.264/MPEG4 pt. 10 AVC standard technology (“Text of ISO/IEC FDIS 14496-10: Information Technology—Coding of audio-visual objects—Part 10: Advanced Video Coding”, ISO/IEC JTC 1/SC 29/WG 11, N5555, March, 2003), which has been developed by a Joint Video Team (JVT) of the ISO/IEC MPEG and ITU-T VCEG groups, general image encoding efficiency may be dramatically improved by performing spatial and temporal prediction encoding in various methods. This standard technology uses an enhanced function, integer transform coding, improves entropy coding efficiency using context adaptive binary arithmetic coding (CABAC), but fails to provide a method of processing an image containing a gray alpha channel image.